But what about bookshelves that start to roll off lower than 80Hz?
Also, wouldn't it be different if the speaker is EQed to a curve that rolls off, vs just having a 12db/oct filter applied on top of the eq? From the way ARC displays it, it seems that the rolloff is in the target curve itself so the speaker supposedly would roll off at 12db/oct after EQ, although we would need measurements to confirm that's how it actually works. In that case I wouldn't expect the acoustic rolloff to add 12db/oct on top of that? I've also seen posts saying that the crossover itself adds another 12db/oct filter on both subwoofer and speakers, so the default 12db/oct slopes from the target curve combine with it to provide a symmetric 24db/oct slopes without changing any settings, which would make your 24db/oct slope become a 36db/oct slope with crossover active.
It would be nice to confirm how things actually work, which would require either Anthem better documenting what Arc does or just someone measuring what it does.
I also couldn't find anything about the subwoofer phase adjustment and the newly added automatic phase adjustments. What they actually change, how to use them, and how the automated system works and how optimal is it compared to other solutions (such as manual adjustments based on REW measurements), and whether the new automatic adjustments does anything that couldn't be done before manually.